[lttng-dev] some troubles having lttgng-ust actually log something on a shared library

[Sébastien Barthélémy]

Hi Mathieu,

thank you for you help, it is much appreciated.

2011/12/16 Mathieu Desnoyers <compudj at krystal.dyndns.org>:
> * Sébastien Barthélémy (barthelemy at crans.org) wrote:
>>
>> using ust debug mode, I noticed this error message:
>>   libust[30999/31001]: Error: futex: Bad address (in
>> wait_for_sessiond() at lttng-ust-comm.c:571)
>
> I changed this so it only shows up if "LTTNG_UST_DEBUG" env var is set

I set that var.

>> a shared library. I probably have missed some obvious step.

> This diff to the makefile makes it work here (you forgot to add
> ust_motion.o to your .so).

That was indeed an obvious step to miss! Indeed it fixes the example
here too, thank you.

Alas, that does not solve my original problem: I'm trying to add
tracing to a bigger application,
for which tracing does not really work yet.

The example I sent was just a attempt to reproduce my problems on a
simpler application.
I guess I was just too happy to reproduce it on such a simple program, that I
sent it to the ML without double checking. Sorry for that (and thank you again).

Back to my original problem now: the application I'd like to add
tracing to loads plugins
(dlopened shared libraries I guess). Tracepoints added to these
plugins are never logged
anywhere. However, traces added to the main executable show up in
babeltrace. I probably
have some link problem again, what do you think?

A better understanding of the way probes are enabled would probably
help me debug it.
Is it documented somewhere? Or could you point me to the right source file?

Thank you again.

Regards
-- Sebastian